To the Editor: Members of the genus Haemophilus are commensal
bacteria of the upper respiratory tract, and H. influenzae is the main
pathogen in this genus that can cause a wide range of human infections
(1). The species most closely related to H. influenzae is H.
haemolyticus, usually considered a commensal of the nasopharynx in
humans; it can be pathogenic, although rarely (2,3). H. parahaemolyticus
was distinguished from H. haemolyticus in 1953 when it was determined
that H. parahaemolyticus required only factor V, but not factor X, for
growth (4). This species could be responsible for pharyngitis and,
rarely, for subacute endocarditis (4), but it has seldom been reported
to cause invasive disease (5). Invasive disease has been reported in a
patient who had an empyema in the gallbladder (6) and in a patient who
had a cryptogenic brain abscess (7). We report a case of acute
respiratory distress syndrome (ARDS) and septic shock caused by H.
parahaemolyticus.

A 50-year-old woman, who was receiving artificial ventilation, was
transferred to the Hopital Nord in Marseille, France, in November 2012.
She was in a coma because she had taken an overdose of benzodiazepine
and clomipramine in a suicide attempt. She had no relevant medical
history except addiction to tobacco, chronic alcoholism, and depression.
The patient's family owned 3 cats and 1 dog but had no other pets.
She had not traveled outside France.

On the second day, a bronchoalveolar lavage (BAL) specimen
(obtained before initiation of antimicrobial drug therapy) was positive
for H. parahaemolyticus ([10.sup.7] CFU/mL) on a chocolate polyvitex
agar plate, and the strain showed susceptibility to
ampicillin/clavulanate, ceftriaxone, gentamicin, and ciprofloxacin. The
bacterium was hemolytic and required factor V, but not factor X, for
growth. The bacterium was identified in the laboratory by
matrix-assisted laser desorption ionization time-of-flight (MALDITOF)
mass spectrometry with the Bruker Biotyper software database (Bruker
Daltonics, Bremen, Germany), with a good score (>2.0) (8). The
identification was confirmed by PCR amplification and sequencing of the
16S rRNA gene (size of sequence was 1,387 bp, and it had 99.6% homology
with sequence AJ295746 in GenBank). Blood culture results were negative
for both bacterial species. The final diagnosis was septic shock
associated with ARDS, due to aspiration pneumonia.

In the ICU, the patient received ampicillin/clavulanate and
gentamicin, along with vasopressor therapy and crystalloid fluid
resuscitation. Her response was dramatic, and her condition improved
rapidly. When she was stabilized and able to take oral drugs, she was
given ampicillin/clavulanate, 1 g 3x daily for 7 days. On day 9, she was
discharged from the ICU in stable condition. One month after discharge,
she attended a follow-up visit at the pulmonary outpatient department
and had made a full recovery.

This study shows the isolation in pure culture of H.
parahaemolyticus from the BAL specimen of a patient with septic shock
with ARDS. The isolate was unambiguously identified by MALDI-TOF (8) and
confirmed by 16S rRNA sequencing. Correct identification of bacteria of
the genus Haemophilus at the species level, including H.
parahaemolyticus, by MALDI-TOF, has also been reported in 2 recent works
(9,10). Isolation of this bacterium in pure culture from the BAL
specimen was eventually associated with the disease of the patient
(including a coma complicated with aspiration pneumonia and bilateral
pulmonary consolidations), and the patient rapidly improved after
receiving antimicrobial drug treatment.

These findings suggest that H. parahaemolyticus was the causative
agent of the patient's disease. Although this bacterium has been
rarely reported as a cause of human infections, it should be considered
as an opportunistic pathogen, especially in patients who have aspiration
pneumonia, because it is likely a commensal of the upper respiratory
tract. Among 31 H. parahaemolyticus isolates from human specimens
reported by Norskov-Lauritsen et al., 75% of the isolates were recovered
as commensals in the pharynx and throat and from sputum (10). This
bacterium was likely overlooked in the past because phenotypic
identification was not sufficiently accurate to distinguish it from
other Haemophilus spp. Thus, H. parahaemolyticus has a pathogenic
potential for causing invasive and severe diseases in humans that should
be further investigated.

DOI: http://dx.doi.org/10.3201/eid1910.130608

Acknowledgment

We thank Linda Hadjadj for technical assistance.

This work was partly funded by the Centre National de la Recherche
Scientifique, France, and L'Institut Hospitalier Universitaire
Mediterranee Infection.

(1.) Peltola H. Worldwide Haemophilus influenzae type b disease at
the beginning of the 21st century: global analysis of the disease burden
25 years after the use of the polysaccharide vaccine and a decade after
the advent of conjugates. Clin Microbiol Rev. 2000;13:302-17. http://
dx.doi.org/10.1128/CMR.13.2.302317.2000

(5.) Kilian M. A taxonomic study of the genus Haemophilus, with the
proposal of a new species. J Gen Microbiol. 1976;93:9-62.
http://dx.doi.org/10.1099/00221287-93-1-9

(6.) Parsons M, Faris I. Empyema of the gallbladder due to
Haemophilus parahaemolyticus, with a brief review of its role as a
pathogen. J Clin Pathol. 1973;26:604-5.
http://dx.doi.org/10.1136/jcp.26.8.604